This study will determine what factors are associated with unsafe sex and undetected HIV infection among a sociodemographically diverse sample of 600 alcoholic adults consecutively admitted to an inpatient rehabilitation unit. Our pilot data on 110 such inpatients suggest that rates of unsafe sex during the month prior to admission are notably high (38%) and that rates of undetected HIV infection are also high (12%). We therefore wish not only to determine if these rates are similarly high among a large sample, but also to identify subject variables associated with both unsafe sex and undetected HIV infection. The results might help clinicians identify alcoholic inpatients who are especially in need of risk-reducing interventions and of voluntary HIV testing with counseling. As in our IRB-approved pilot studies, the absolute prevalence of HIV infection will be determined using waste admission bloods tagged with only selected demographic and clinical variables that preclude identification of a given patient. The detected prevalence of HIV infection will be determined by chart review. "Undetected HIV infection" will be defined as the difference between absolute and recorded HIV infection. As in our other studies of over 1000 subjects, unsafe sex and other HIV-related risk behavior during the past month will be assessed by a HIV Risk Behavior Questionnaire. Guided by the HIV literature and pilot data, multivariate analyses will examine for hypothesized measured variables associated with unsafe sex, including comorbid mental illness, comorbid drug use disorder, personality traits, and addiction severity. Although this 2-year small grant will in itself provide useful information regarding an understudied population, the study is also seen as providing necessary data for a more ambitious intervention study to reduce HIV transmission among alcoholic adults.